Treatment of tobacco



United States Patent 3,306,307 TREATMENT OF TOBACCO Geoffrey NormanRichards, Townsville University,

Queensland, Australia, assignor to American Machine & Foundry Company,New York, N.Y.

No Drawing. Filed Apr. 15, 1965, Ser. No. 448,251 Claims priority,application Great Britain, Apr. 17, 1964, 15,982/64 2 Claims. (Cl.131-140) This invention relates to the production of reconstitutedtobacco sheet from tobacco stems.

Reconstituted tobacco sheet is norm-ally made by cooking tobacco ortobacco stems with Water at elevated temperature (usually above 135 C.),mechanically refining to a pulp, perhaps adding tobacco dust, and thencasting to a sheet on a steel belt. The economic necessity to obtain ahigh yield normally excludes the possibility of washing out solu'blesfrom the pulp or sheet and the finished sheet product obtained by such amethod is a very dark brown in colour. While this colour is notdetrimental to use of the sheet as cigar binder, it precludes its use incigarette filler.

We have concluded that at least part of the dark colour of the sheetresults from complex reactions such as sugar browning during the sterncooking process. These reactions result, for example, from interactionof reducing sugars and amino acids, and are known to be highly dependenton temperature and pH. We have now found that the colour formingreactions can be suppressed to an adequate extent by adopting any one ormore of the following procedures viz.

(1) The stem cooking temperature is reduced to 110 to 130 C. withsufficient increase in refining (i.e. beating) time to produce adequatepulp freeness.

(2) The time of cooking is reduced e.g. to less than 2 hours at 140 C.ranging to less than 4 hours at 130 C. again with longer refiningperiod.

(3) A small amount of acetic acid is added to the cooking liquors, inwhich case the period of refining may be reduced in comparison with thesame procedure but without acetic acid. The quantity of acetic acid is 1to 10 percent (preferably 2 to 7 percent) based on tobacco solids.

Furthermore, we have found that the stem pectic acid (which is animportant factor in sheet strength) is very much less degraded bycooking at these lower temperatures and that the use of acetic acidspeeds up the subsequent refining of the stems and hence reduces thepower requirements for this operation.

The advantages achieved by this invention are illustrated by thefollowing examples:

Cooking stems (1) 225 g. bright stems (moisture 11.1%) were cooke'dwit-h 1650 ml. water at 15 p.s.i.g. (pounds per square inch) (121 C.)without stirring for hours.

(2) Experiment 1 was repeated with 1650 ml. of 0.0885 N acetic acid inplace of the water.

(3) Experiment 1 was repeated at 40 p.s.i.g. (141 C.) in a rotatingautoclave for 5 hours.

Beating stems In each case, after cooking, the stems and extracts werediluted to 3300 g. with water and beaten in a Medway 'beater afterslushing for about 5 minutes. The changes in Canadian Standard Freenesswith beating time for experiments 1 and 2 are shown in Table II. Inexperiment 3, the stems were so soft that heating to the increasing CSFstage occurred during slushing and the pulp was ultimately obtained atCSF 550. The beaten pulps from experiments 1 and 2 were much moreviscous than those from 3,306,307 Patented Feb. 28, 1967 experiment 3.This elfect is probably related to the degradation of pectic acid in thelatter experiment (see Table 1).

Casting sheets A g. sample of pulp from the beater was stirred with 12g. air-dry tobacco leaf dust ('80 mesh fraction) and 20 ml. water,de-gassed at 30 pressure for 10 minutes and cast on a Teflon-coatedstainless steel plate with a knife or doctor blade providing a spreadinggap of 0.05. The sheet was placed in a stream of air in an oven at 150C. and removed just before drying was complete. In all cases the topsurface of the sheet was much darker than the lower.

The sheet from experiment 3 was very dark in colour, that fromexperiment 1 was less dark, while the sheet from experiment 2 was by farthe lightest in colour.

Pectic acid in the pulps The pulps from experiments 1-3 were eachcentrifuged and samples of the clear brown centrifugates tested fordissolved pectic acid by addition of calcium chloride solution andhydrochloric acid. In no case was any gel precipitated, and it wasconcluded that no dissolved pectic acid was present in the pulps.

10 g. ammonium oxalate was then added to 500 g. samples of pulp fromexperiments 1 and 3, and boiled with stirring for 2 hours. The pulpswere next centrifuged and the centrifugates stirred at room temperaturewhile 10 ml. of concentrated hydrochloric acid was added. Experiment 1yielded a gel precipitate at this stage while experiment 3 yielded afiocculent powder precipitate. The pectic acid products were washed withacetone and viscosities were determined. Results are tabulated in TableI and show that the pectic acid is not unduly degraded during 5 hours at121 C. but is heavily degraded at 141 C.

TABLE I.PROPERTIES OF PECTIC ACID FROM COOKED BRIGHT STEMS 1Concentration 0.25% in 0.155 M. sodium chloride at pH 6.0.

TABLE II.REFINING OF COOKED BRIGHT STEMS Beating Time (min.) PulpFreeness (A) (CanadiaFBtandard) (A) Cooked in water at 121 for 5 hours.

(B) Cooked in 0.885 N acetic acid for 5 hours.

Not determined.

These figures show that the use of acetic acid is also of greatadvantage in obtaining an adequate pulp freeness within a reasonablebeating time.

What I claim is:

1. A method for the production of reconstituted tobacco sheet comprisingthe steps of cooking tobacco stems in water at a temperature between 120C. and C. for periods ranging from two hours at 140 C. to about fivehours at 120 C. followed by diluting with water and slushing and thenmechanically beating the resultant pulp for about five minutes toproduce a refined pulp having pulp to produce a refined pulp havingadequate freeness, adequate freeness, and thereafter forming the pulpinto and ther after f rming the pulp into a Sheet.

a sheet.

2. A method for the production of reconstituted tobacco References Cltedby the Exammer sheet comprising the steps of cooking tobacco stems in 5UNITED STATES PATENTS water containing 1 to 10% by weight of acetic acidbased 2,485,670 10/1949 So et 1 131 140 on tobacco solids at atemperature between 120 C. and 3,020,179 2/1962 Hess 131140 140 C. forperiods ranging from two hours at 140 C. to five hours at 120 C.,thereafter diluting with water SAMUEL KOREN Prlma'y Examine" andslushing and then mechanically beating the resultant 10 MELVIN D. REIN,Examiner.

1. A METHOD FOR THE PRODUCTION OF RECONSITITUTED TOBACCO SHEETCOMPRISING THE STEPS OF COOKING TOBACCO STEMS IN WATER AT A TEMPERATUREBETWEEN 120*C. AND 140*C. FOR PERIODS RANGING FROM TWO HOURS AT 140*C.TO ABOVE FIVE HOURS AT 120*C. FOLLOWED BY DILUTING WITH WATER ANDSLUSHING AND THEN MECHANICALLY BEATING THE RESULTANT PULP FOR ABOUT FIVEMINUTES TO PRODUCE A REFINED PULP HAVING ADEQUATE FREENESS, ANDTHEREAFTER FORMING THE PULP INTO A SHEET.